Snowmobile triggered slide in Taylor Fork today from above cutting across. Nobody caught. 2.5 feet deep 150 feet wide
<p>In the mountains around Cooke City, Island Park, and West Yellowstone, including the Southern Madison and Southern Gallatin Ranges, strong winds will drift recent snow, loading slopes where triggering <strong>wind slab avalanches </strong>that break 1-2 feet deep<strong> </strong>are likely. Continued snowfall and increasing winds will exacerbate this instability today. On Thursday, snowmobilers in Island Park reported that drifted snow and cornices cracked and collapsed easily on test slopes (<a href="https://www.mtavalanche.com/node/34706"><span>observation</span></a>). Avoid steep terrain where active drifting, cornices and shooting cracks indicate instability. Select slopes sheltered from the wind—often found at middle and low elevations where the trees block the wind—for safer avalanche conditions.</p>
<p>In the Lionhead area, and Southern Madison and Southern Gallatin Ranges, weak layers buried in late January continue to result in infrequent <strong>persistent slab avalanches</strong>. The most recent slide in the Taylor Fork occurred Wednesday and broke 2-4 feet deep (<a href="https://www.mtavalanche.com/node/34697"><strong><span>details</span></s…;). These layers have not resulted in avalanches in the Centennial Range, but snowmobilers assessing for instability noted a weak layer buried two feet deep below a melt-freeze crust that broke and propagated in unstable test results. Manage the problem of avalanches failing on persistent weak layers by selecting less consequential terrain (smaller slopes with fewer terrain traps) and following safe travel practices (beacon, shovel, probe, and traveling one at a time on steep slopes). Testing for instability can reduce, but will not eliminate, the chances of a surprise.</p>
<p>The danger is CONSIDERABLE on wind-loaded slopes and MODERATE on all others.</p>
<p><span><span><span>Windy conditions in the mountains around Bozeman and Big Sky will cause the limited snow available for transport to drift into slabs that could avalanche on steep slopes. The terrain immediately below cornices and on upper-elevation slopes loaded by west and southwest winds is the most likely area to trigger a <strong>wind slab avalanche</strong>, breaking 6 inches to a couple of feet deep. On Wednesday, a skier was caught and carried 100 feet down a steep slope south of Bridger Bowl, serving as a poignant reminder of the power of a relatively small slide (<a href="https://www.mtavalanche.com/node/34703"><strong><span>details and video</span></strong></a>). Yesterday in Beehive Basin, Ian recommended identifying and avoiding wind-loaded slopes and digging down a couple of feet to test for instability, reducing the chances for surprises if you are considering travel in steeper terrain (<a href="https://www.mtavalanche.com/node/34715"><strong><span>observation and video</span></strong></a>). Shooting cracks and recent avalanche activity are the most precise indicators of instability. </span></span></span></p>
<p><span><span><span>Seek out terrain sheltered from the wind where avalanche conditions are generally safe, and slides are unlikely. The danger is MODERATE on wind-loaded slopes and LOW on all others. </span></span></span></p>
Took a quick trip up Beehive Basin to the prayer flags, down into the meadows towards Bear Basin and returned the way we came.
Found around 4" of new snow from yesterday. There were scoured areas near the ridgeline on the west face, but we didn't find any cohesive wind drifts.
We dug two quick pits on the east facing terrain dropping towards Bear Basin. In our upper pit (NE aspect, 9200 ft), we found a layer of small facets (1 mm) buried a foot down, under the snow that has fallen in the past week. It didn't react in our Extended Column Test (ECTN25), but we hadn't had any reports of these facets previously, so it was a little bit surprising. We dug again, a little lower (~8900) to see if we would find it again, but it didn't exist in that location (instead there was a stout melt-freeze crust under this weeks snow).
There was a thin, breakable, melt-freeze crust under yesterday's 4" of new snow on any slope that wasn't a little shaded. Slopes with a northward tilt, or in the shade of trees, didn't have the breakable crust.
Despite high clouds, the snow surface was starting to get damp in the early afternoon and there were roller balls beneath our ski tracks. We saw a fresh wet loose slide on an low elevation west facing slope in Bear Basin.
Otherwise, we saw no signs of instability.
From text message: “I was out with a friend and his 2 daughters. We were east of Jefferson 8990’ elevation. East aspect ECTP 22. Down 78cm from surface. Melt freeze layer I would describe as breaking up?? garbage.”
<p><span><span><span><span><span><span>Around West Yellowstone, Island Park and Cooke City, 3-4” of new snow yesterday along with strong gusty winds built touchy wind slabs that will be easily triggered today. Riders in Island Park yesterday reported heavy snowfall, strong winds, and touchy wind slabs and cornices (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34706"><span><span><span><span><span><…;). </span></span></span></span></span></span><span><span><span><strong><span><span>Wind Slab avalanches </span></span></strong></span></span></span><span><span><span><span><span><span>are most likely to break in the newly formed drifts, but could also break into deeper drifts from the multiple feet of snow that fell last weekend. These drifts are mostly at upper elevations, below ridgelines and cornices.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>In addition to wind drifts, near West Yellowstone, you could also trigger a slide on deeper persistent weak layers. You aren’t super likely to trigger a </span></span></span></span></span></span><span><span><span><strong><span><span>Persistent Slab avalanche </span></span></strong></span></span></span><span><span><span><span><span><span>today as we’ve only had two reports of these slides in the last three weeks. But, the snowmobile triggered slide in the Taylor Fork on Wednesday shows it is clearly still possible (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34697"><span><span><span><strong><span…;). Thinner snowpacks at mid-elevations seem to be the prime suspects for these slides. </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Today, wind loaded slopes have a CONSIDERABLE avalanche danger. All other slopes have a MODERATE danger.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>The Big Sky area was the big winner in yesterday’s snowfall, with up to 8” of new snow. Fresh </span></span></span></span></span></span><span><span><span><strong><span><span>wind slabs </span></span></strong></span></span></span><span><span><span><span><span><span>will be up to a couple feet deep and easily triggered today. Keep your eyes out for signs of wind drifting and plan to avoid steep wind-drifted slopes. Pay careful attention to the texture of the snow beneath your feet or sled if you’re riding steep slopes that don’t seem wind affected. Cracks shooting out in front of you mean that the snow is in fact drifted and you need to get out of steep terrain ASAP.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>The avalanche danger is CONSIDERABLE on wind loaded slopes. Slopes sheltered from the wind have good stability and a LOW danger.</span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>Less new snow fell in the mountains around Bozeman, so fresh </span></span></span></span></span></span><span><span><span><strong><span><span>wind slabs</span></span></strong></span></span></span><span><span><span><span><span><span> will be smaller and less widespread. Look for the same signs of wind drifting and be ready to back off steep slopes if you find unstable drifts. A skier caught and carried 100 ft on Wednesday in the Bridgers is a good reminder of the power of even a relatively small slide (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/34703"><span><span><span><strong><span… and video</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Slopes at higher elevations, beneath ridgelines and cornices are where you’re most likely to run into issues. </span></span></span></span></span></span></p>
<p><span><span><span><span><span><span>The avalanche danger is MODERATE on windloaded slopes and LOW on all other slopes.</span></span></span></span></span></span></p>
Skied a lap on Texas Meadow north of Bridger this afternoon. There were about 2" of new snow from today and 10-12" settled new snow that fell since last Friday. A few moderate gusts moved snow, but wind was not generally light. There was minimal fresh drifting, limited to ridgelines and openings in the trees.
A lot of ski tracks off the ridge north of the ski area. Only small loose snow slides were triggered from what I could tell, under mostly cloudy skies.
Snowpit at 7700', NE aspect showed a 6 foot deep, stable snowpack (profile attached). New snow creates the main avalanche concern, mainly where it is drifted into stiffer slabs. Dry Loose snow avalanches are a second concern for now.
